This invention relates generally to signal processing and in particular to signal processing utilizing switch capacitor circuits.
As is known, switch capacitor circuits are used in a variety of applications. One such application is within an over sampling analog to digital converter. Such an over sampling analog to digital converter includes an over sampling front-end quantizer and a digital decimation filter. The over sampling front end quantizer may be a Sigma Delta modulator that includes switch capacitor circuits. The switch capacitor circuits are utilized to sample an input voltage with respect to reference voltages and to provide the sample to an operational amplifier and comparator. Based on this sampling, the front-end quantizer produces a high-speed single bit digital output stream, via the operational amplifier and the comparator. The digital decimation filter receives the high speed single-bit digital data stream and converts it into digital words.
In most over sampling analog to digital converter applications, the analog input is AC coupled to the analog to digital converter. As such, the DC components of the input signal are rejected thereby avoiding common mode issues. As a result, the reference voltages utilized within the switch capacitor circuit are the same. However, such an implementation does not provide the optimum common mode solution needed in certain applications where the analog input is DC coupled to the analog to digital converter.
Therefore, a need exists for an improved switch capacitor circuit that compensates for common mode issues such that the improved switch capacitor circuit may be utilized in a variety of applications, including analog to digital converters.